Performance of a digital PCO2/SPO2 ear sensor

J Clin Monit Comput. 2004 Apr;18(2):75-9. doi: 10.1023/b:jocm.0000032693.78829.42.


Objective: For determining the adequacy of ventilation, conventional pulse oximetry should be amended by PaCO2 (= arterial carbon dioxide partial pressure). This study investigates the precision of carbon dioxide measurements of the first digital ear-clip sensor providing continuous non-invasive monitoring of PaCO2, SpO2 (= functional arterial oxygen saturation as estimated with a pulse oximeter) and pulse rate and compares it to two conventional analog oximeters.

Methods: 30 hypoxemia episodes in 6 adult volunteers were investigated in a standardized protocol.

Equipment: Masimo analog finger sensor, Nellcor analog ear sensor, SenTec digital ear sensor.

Results: The difference between PCO2 data (= PaCO2 estimated from the measured PcCO2 based on an algorithm by Severinghaus) (PcCO2 = cutaneous carbon dioxide pressure) and the PaCO2 is clinically unimportant. Therefore, we suggest, the two methods of estimating patient's carbon dioxide status can be used interchangeably.

Conclusions: Combined digital SpO2/ PcCO2 ear sensors are very promising to allow for a fast and reliable monitoring of patient's oxygenation, hyper-/hypocapnia and ventilation with one single non-invasive probe. Optimal primary signal processing--amplification and digitalisation within the probe--allow for fast and reliable downstream signal processing algorithms. The resulting short SpO2 response times give the medical staff more time to take appropriate actions.

Publication types

  • Clinical Trial

MeSH terms

  • Adult
  • Algorithms*
  • Carbon Dioxide / blood*
  • Ear
  • Equipment and Supplies
  • Female
  • Fingers
  • Humans
  • Hypoxia / diagnosis
  • Male
  • Oximetry / instrumentation*
  • Oxygen / blood*
  • Respiration
  • Sensitivity and Specificity
  • Signal Processing, Computer-Assisted*


  • Carbon Dioxide
  • Oxygen